Most liquid crystal display (LCD) devices are passive devices in which images are displayed by controlling an amount of light inputted from an external light source. Thus, a separate light source (for example, backlight module) is generally employed for illuminating an LCD panel.
Generally, backlight module includes a light source, a light guide plate, a reflective sheet, and a diffusion sheet. The light guide plate includes a light incident surface, a light emitting surface adjoining the light incident surface, and a bottom surface facing an opposite direction of the light emitting surface. The light source is located adjacent to the light incident surface of the light guide plate. The light guide plate is located between the reflective sheet and the diffusion sheet with the bottom surface adjacent to the reflective sheet and the light emitting surface adjacent to the diffusion sheet. When light produced by the light source is emitted into the light guide plate, the light guide plate redirects the light. The reflective sheet reflects the light scattered towards the reflective sheet back towards the light guide plate to increase utilization efficiency of light energy. The diffusion sheet diffuses the light emitted from the light guide plate, thus, a brightness of the light incident on the LCD panel would be more uniform.
One kind of light guide plate is illustrated in FIGS. 1 and 2. A light guide plate 10 includes a light incident surface 11, a light emitting surface 12 adjoining the light incident surface 11, and a bottom surface 13 facing an opposite direction of the light emitting surface 12. In order to improve optical uniformity, a plurality of patterned dots 131 is formed at the bottom surface 13. Light produced by a light source (not shown) is emitted towards the pattern dots 131 via the light incident surface 11. Light is scattered by the patterned dots 131 before emitted out the light emitting surface 12 of the light guide plate 10. However, the light guide plate 10 has difficulties emitting light to project approximately in a perpendicular direction of the light emitting surface 12, thus decreasing the brightness of the emitted light.
Another kind of light guide plate is illustrated in FIGS. 3 and 4. A light guide plate 20 includes a light incident surface 21, a light emitting surface 22 adjoining the light incident surface 21, and a bottom surface 23 facing an opposite direction of the light emitting surface 22. In order to obtain a uniform light energy distribution, a plurality of V-shaped structures 221 are formed on the light emitting surface 22. The V-shaped structures 221 extend out of the emitting surface 22 regularly and periodically in a direction parallel to a Y-axis and parallel to each other. Light produced by a light source (not shown) is guided towards the V-shaped structures 221, and most of the light guided towards the V-shaped structures 221 is then refracted by the V-shaped structures 221. The light guide plate 20 is able to project the refracted light at approximately a perpendicular direction to the V-shaped structures 221. That is to say, the refracted light is substantially aligned with the Z-axis in a XOZ coordinate system. However, the light guide plate 20 is easy to generate Newton ring interference action because the V-shaped structures 221 extend out of the emitting surface 22 regularly and periodically in a direction, thereby decreasing the optical uniformity.
Therefore, a new light guide plate and a backlight module using the same are desired in order to overcome the above-described shortcomings.